The U.S. prison population has declined in the past few years but the incarceration rate is still the highest in the world. Prison overcrowding is a serious problem in several states, especially California. The federal government is weighing in on the issue too.

ATTORNEY GENERAL ERIC HOLDER: I think there are too many people in jail for too long and for not necessarily good reasons.

MARTIN: That was U.S. Attorney General Eric Holder. In an interview with NPR earlier this year, he discussed how the country's drug policies have led to mass incarcerations.

HOLDER: The war on drugs is now 30, 40 years old. There have been a lot of unintended consequences. There has been kind of a decimation of certain communities, in particular communities of color.

MARTIN: Tomorrow, the attorney general is scheduled to give a speech in San Francisco about plans to reform the criminal justice system. He's expected to outline changes to minimum sentencing laws, in hopes of reducing the number of people put away for low-level drug charges.

We thought it was a good time to look back on the drug war - what has worked and what hasn't. To help us do that, we reached out to Craig Reinarman. He's a sociology professor at the University of California, Santa Cruz. And he said that the war on drugs started with President Richard Nixon.

CRAIG REINARMAN: Nixon and the Republicans ran on a law and order campaign. And the war on drugs was a way for Nixon to appeal to a core, more conservative, suburban white constituency. And it was seized upon as an opportunity to clamp down on a lot of things they wanted to clamp down on anyway, and it was used to that effect.

MARTIN: Subsequent administrations use that phrase: The war on drugs. Ronald Reagan is often associated with aggressive drug policies. What was his legacy when it comes to the war on drugs?

REINARMAN: Well, it turns out that crack cocaine made its emergence in the mid-Reagan years, and Reagan jumped on it under the idea that this was a new and startlingly dangerous substance, the likes of which we've never seen before, most addictive drug ever known and all of that. None of that turned out to be true but at the moment of national hysteria in 1986, '87, Congress passed and Reagan signed laws that created these long mandatory minimum sentences for the possession of small amounts of crack cocaine, that led to the largest wave of imprisonments in American history.

MARTIN: Why did that happen? How did the emergence of crack cocaine really change things?

REINARMAN: Well, crack cocaine is just cocaine that is vaporized and inhaled in base form, but it's a different way of using the drug. And, you know, rich people had been doing that for quite a while - rock stars and Wall Street people, professional sports people, people with a lot of money. The thing that was innovative about crack was it was sold in much smaller units, cheaper units, on street corners in the inner cities. And so, it became a dangerous drug, became associated with a dangerous class.

MARTIN: What do you think are the appropriate ways to measure how drug policies work, how effective they are? If it's not incarceration rates or the rates of arrest for infractions of drug laws, what are the more appropriate metrics?

REINARMAN: It's a very great question to ask about metrics because very often you hear a record bust, you know, two tons of this or that drug stopped at the border. But we don't know what percentage of the total it is. In other words, we don't have the denominator in that fraction so we don't know whether, you know, stopping two tons is 2 percent or 20 percent.

But if you ask users, a great majority of them don't ever seem to have any trouble finding a supply when they want one. There's a lot of reasons for that. But the principal logic behind it is if there's a demand for a substance that is prohibited, somebody is going to be willing to take the risk because there are huge profits to be made.

MARTIN: Is there a way to measure how far we have come with the war on drugs? When we think back to the early '70s and Richard Nixon's initial declaration, have things gotten better over all of these decades?

REINARMAN: Well, it's interesting. It depends on who you ask. It's true that the proportion of the population who have used illicit drug in their lives, or even recently, is lower than it was in the late 1970s, early 1980s when drug use in a generation peaked. But whether it has anything whatsoever to do with drug policy and all these arrests is another matter.

We seem to be at a point now, an inflection point, where more and more people on both sides of the political aisle are realizing that we cannot incarcerate our way out of our drug problems, particularly following the financial crisis, where state governments are just strapped, especially California but not - including many, many others. They realize they just can't afford to just to keep locking up so many people for so long, for usually very minor drug busts.

MARTIN: So does that mean that as a society, barring legalization of all illegal drugs, do we just have to accept some larger-level problem in our country when it comes to drug use?

REINARMAN: Whether we want to accept it as a moral matter or not is a separate kind of question. But it's a historical fact that it exists. We, as a society, use more drugs than any other society on Earth and that's been true for quite a while. It has something to do with affluence, it's something to do with individualism and our mass consumption culture.

So I think we have to accept that nobody is going to create a drug-free society. That's a complete myth. We are a drug-besotted society. The question is how you can reduce the harm that these drugs do and get people the help that they need, so that they don't do more damage to themselves or their families or their communities.

MARTIN: Craig Reinarman is a sociology professor at the University of California in Santa Cruz. He spoke to us from Santa Cruz.